Close, but if it was , then the period would be so the half period (which is what is shown) should be wide, but in the graph it extends from 0 to 2. To fix it we can scale the function by a factor of . To do so requires replacing with , giving:

thanks I got it but now I cant calculate the approximate mean square error, does anyone can help me, I know I´m doing something worng because the valeu I got is -16 as should be 0,xx because it is a percentage.